Regulatory compliance - thermoplastic rooflights

Workplace (Health Safety and Welfare) Regulations 1992 state – “Every workplace shall have suitable and sufficient lighting which shall, so far as is reasonably practicable, be by natural light”. These comments are restated in HSG38 – Lighting at Work.

The most effective method of providing even, consistent daylight, particularly in large buildings, is through rooflighting – up to three times more efficient than windows of a similar area. Diffusing materials should be used wherever possible to provide even light distribution and avoid glare. Wall glazing is less effective and can create internal shadows and dark corners. However it does offer good psychological benefits and must not be ignored.

In the UK, Building Regulations Approved Document B (2006 edition amended 2007) sets out the rules for fire safety of buildings. Section B2 covers internal fire spread, and applies to the linings of both the roof and walls of buildings. In general these are surface spread of flame requirements to BS476 Part 7 (typically Class 1 and Class 3) or to BS EN 13501 Part 1 (typically Class C-s3,d2 or Class D-s3,d2). Section B4 covers external fire spread and applies to external coverings or roofs and walls; in general these are fire resistance requirements to BS476 Part 3 (typically AA and AB) or to BS EN 13501 Part 5 (typically BROOF(t4)).

Thermoplastic materials cannot be tested to BS476 Part 3, as the material melts during the test. Building Regulations define an alternative classification method for these materials:
Polycarbonate at least 3mm thick, PVC (any thickness), and multiwall polycarbonate which is rated Class 1 to BS476 Part 7, are given the rating Tp(a).
Other thermoplastic materials can be tested to BS2782, and given ratings of Tp(a) or Tp(b).
Polycarbonate or PVC which achieves Class 1 when tested to BS476 Part 7 or Class C-s3,d2 when tested to BS EN 13501 Part 1, can also be regarded as having AA or BROOF(t4) designation.

For further information, consult the NARM technical committee:

Thermal performance
Independent research has shown that rooflights make a positive contribution to compliance with Part L of the Building Regulations. Full Guidance on use of Rooflights to help meet these requirements is given in NARM document “Designing with Rooflights: Supporting the Guidance in AD L2A & L2B (2010)”, which is a second tier document referenced from Approved Document L, and approved by the Department for Communities and Local Government.

When specifying rooflights, designers should consider carefully the potential to eliminate or reduce known or predictable hazards. The decision on how best to specify rooflights should take account of the risks associated with temporary gaps during construction, and the risks when access to the roof is needed later e.g. during maintenance or cleaning.

As in all building work good safety standards are essential to prevent accidents. In accordance with the Health and Safety at Work Act and the Construction (Design and Management) or CDM Regulations 2007 , the building should now be designed with safety in mind, not only for the construction period but throughout the normal life of the building. This must include considering the safety of people involved in maintenance and repair, and even demolition. It might mean providing permanent access to the roof, walkways and parapets, for example. The HSE document HSG 33 Safety in Roof Work refers specifically to fragile rooflights as an example of a potential hazard to be considered and to be avoided as far as possible.

Construction of the roof is one of the most hazardous operations because of the potential for falls or material dropping onto people below. The roofing contractor must plan and document a safe system of work before starting construction. This must take into account if any of the roof assembly will be fragile until fully fixed. Metal roofing systems together with appropriate rooflights, even after the first fix of lining out, can be designed to be non fragile. However until the systems are fully fixed, both metal and rooflights must be regarded as fragile.

Where specifying rooflights designers should consider the following options:

Specifying in plane rooflights that are non-fragile.
Fitting rooflights designed to project above the plane of the roof, and which cannot be walked on (these reduce the risk but they should still be capable of withstanding a person falling onto them).
Protecting rooflight openings e.g. by means of mesh or grids fitted below the rooflight or between the layers of a built-up rooflight.
Specify rooflights with a design life which matches that of the roof, taking into account the likely deterioration due to ultraviolet exposure, environmental pollution, and the internal and external building environment.


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